OS MTM MLTL Build Thread

[Carrick1973]

Well, after reading about bungelo_ed's new speakers, I decided to take the plunge and build a pair for the LR mains in our living room. I ordered two of the OS MTM kits from Meniscus as well as the OS Center Channel kit (as well as a new Marantz 7.1 80w receiver from A4L!), and the whole enchilada should be here tomorrow afternoon. I've also recently ordered the plans for the Table Tuba from Bill's site and will eventually add that into the mix.

Here is my take on the speaker (a copy of bungelo_ed's version, but instead of a square box, I decided to make it more of a hexagonal shape.


I plan on making it out of 1/2" G2S cabinet grade maple faced plywood sides with a 3/4" cherry faced baffle. Because I'm using 1/2" plywood instead of 3/4" MDF, I'll probably put in two window braces at uneven spacing. Any problems with the shape as it currently stands? Not shown in the drawing yet is the round-over on the very front baffle (1/2" round-over bit) and smaller round-over on the longer baffle (1/4" bit). I'll be sure to take plenty of pictures while I build it, because I've found this forum so helpful in the past while I was just starting out.

[ReissM]

Re: OS MTM MLTL Build Thread

I really like your take on this design. Looks great.

[bungelow_ed]

Re: OS MTM MLTL Build Thread

Wow, mine was intended to be a proof of concept build. You are taking it to the next level. Your drawing looks great from what I see and the dimensions look right.

From an MLTL perspective, the key dimensions are tube length, cross sectional area, driver height/spacing, port location and window brace to locate stuffing. If those parameters remain the same you shuld be in great shape.

I am looking forward to following your build and hearing your listening impressions.

[fastbike1]

Re: OS MTM MLTL Build Thread

Except that the window braces will probably change the cross-sectional area.

Wow, mine was intended to be a proof of concept build. You are taking it to the next level. Your drawing looks great from what I see and the dimensions look right.

From an MLTL perspective, the key dimensions are tube length, cross sectional area, driver height/spacing, port location and window brace to locate stuffing. If those parameters remain the same you shuld be in great shape.

I am looking forward to following your build and hearing your listening impressions.

[Carrick1973]

Re: OS MTM MLTL Build Thread

Except that the window braces will probably change the cross-sectional area.

Agreed - the area still works out to 37.125" square, so the volume is the same. Is that what your comment referred to? Or do you mean the extra window brace itself will take up some volume?

[bungelow_ed]

Re: OS MTM MLTL Build Thread

Except that the window braces will probably change the cross-sectional area.

It would be better to build the boxes from 3/4", as this is a, one example, proven implementation. My proof of concept has one brace. If the braces are built like mine, I don't believe two will have a serious effect on performance, if any at all.

For the record, mine are set in a 3/8" dado and have a rectangular window leaving 1-3/8" to the outside edges. With the increase in side of your design, panel widths will be less too.

[Carrick1973]

Re: OS MTM MLTL Build Thread

Well, after getting all the parts, I started putting it together. After making a couple of sketches in Sketchup in order to get the angles and lengths right, I got some 1/2 MDF and some curly maple from a local store. One trick to maximizing sheet usage is to make your cut, flip one of the resultant boards 180 degrees end-over-end and when you put them together, they form the correct angle. Let me show you an example. If I wanted to put together two sides to form 135 degree angle, I'd divide the 135 by 2 to get 67.5 degrees. Subtracting 67.5 from 90 gives you the setting you should make on your table saw in order to make the right cut, so in this case, you'd set your TS to 22.5 degrees. Make the cut, flip one of the resultant boards 180 degrees end over end and put the cuts together and voila, you've just formed your 135 degree angle.

Here's a picture.


Since I'm making two speakers (L/R) I need to to make 4 of each side part, and two fronts and two backs. Instead of making each cut independently, I'll setup the TS and then make all the cuts for that particular part. This makes sure that all parts are made the same way so that each side is a mirror of itself, and each speaker is identical.

Once all the parts are cutout, I'll arrange them in order with the baffle in the middle, and each side laid out on either side of the baffle. To glue up, I use a hot glue gun to create an inside 'hinge' between two sides. This does two things, it creates a sound-proof seam in the insides of the speaker, and it aligns up the sides for glue-up. Once the hot glue has cooled, I'll open the two sides using the hinge and put a bead of glue along the edges. Closing the hinge, puts enough pressure on the edge for tight seams. Here's a picture that might help. In this picture, I'm gluing up the side on the right side of the picture. I've put a bead of glue between the two pieces and closed up the hinge. I've used scraps of wood from the wood baffle to keep pressure on it until the glue dries.



And finally, here's a picture of the wooden baffle that I'm using on these speakers. The red ink is where I'm going to route out a recess between the bolts in order to allow the sound to escape backwards from the speaker.



I hope this makes sense, but if it doesn't, please feel free to ask any and all questions.

[fastbike1]

Re: OS MTM MLTL Build Thread

Neither. Depending on how you configure the window brace, it can have a detrimental impact on the quarterwave action. I was once chided by an experienced TL builder for using open pane window braces because they changed the cross sectional area for the wave.

Agreed - the area still works out to 37.125" square, so the volume is the same. Is that what your comment referred to? Or do you mean the extra window brace itself will take up some volume?

[Randall Kepley]

Re: OS MTM MLTL Build Thread

Looking great so far, Im looking forward to watching this unfold , keep those pix coming. R.K.

[Carrick1973]

Re: OS MTM MLTL Build Thread

For those following along, here are a couple of drawings with dimensions:

[Birdrider]

Re: OS MTM MLTL Build Thread

Looks like things are coming along nicely. I'm contiplating these as my next build. Question, how did you do the curve on the top and bottom of the mounting plate for the speakers?

[bungelow_ed]

Re: OS MTM MLTL Build Thread

Once all the parts are cutout, I'll arrange them in order with the baffle in the middle, and each side laid out on either side of the baffle. To glue up, I use a hot glue gun to create an inside 'hinge' between two sides. This does two things, it creates a sound-proof seam in the insides of the speaker, and it aligns up the sides for glue-up. Once the hot glue has cooled, I'll open the two sides using the hinge and put a bead of glue along the edges. Closing the hinge, puts enough pressure on the edge for tight seams. Here's a picture that might help. In this picture, I'm gluing up the side on the right side of the picture. I've put a bead of glue between the two pieces and closed up the hinge. I've used scraps of wood from the wood baffle to keep pressure on it until the glue dries.

Very interesting approach, which I will store away for my bag of tricks. I would have taken a different approach, which relies on the top, bottom and window brace to locate the sides with dados. Probably no better or worse, just a different approach.

Looking forward to more pictures and detailed explanation of how you build the cabinets. great job!

[Carrick1973]

Re: OS MTM MLTL Build Thread

Hey Birdrider,
It's actually pretty easy. I first marked the center of the board by connecting each opposite corner with a line. Once center was established, I made a 1/16" inch hole at center with my drill press (a normal drill could be used for this). Next I put a brad into the hole (this is done before the tweeter cutout, of course) and used a string and pencil as a compass to mark off the circle. Using a scrollsaw or jigsaw, cut the circles near the outside of the line to cut off most of the waste. Next up, you can either use a sanding drum in a drillpress to ease up on the line, or, as in my case, use a router for the final dimensioning. The way I did this was make a hole in my router table at exactly 7.5" to the inside of the router bit. The brad that was used for the compass is now used as a swivel point on the router table. By swiveling the baffle around the center swivel point, you take off the final bit of waste, cleaning up the edges.

Hope this makes sense. If not, I'll take a picture later on in order to help out. I do this same thing when routing out the recesses for the speakers as well, but when doing that, you want to measure to the outside of the router bit, not the inside of the router bit.

[Birdrider]

Re: OS MTM MLTL Build Thread

Well I put in an order for all the MTM components. I'm not sure if I'll do one of these or the original yet but I've got them ordered.

Question, if I'm planning on doing a subwoofer would there be any advantage to doing these?

[bungelow_ed]

Re: OS MTM MLTL Build Thread

Well I put in an order for all the MTM components. I'm not sure if I'll do one of these or the original yet but I've got them ordered.

Question, if I'm planning on doing a subwoofer would there be any advantage to doing these?

If you want to use a sub-woofer I would build the original design. The TL is best suited to music duty where bass demands are not lower FR than typical acoustic instruments.

If you are planning to use the OS MTM for HT or loud music featureing alot of bass content, then a sub-woofer is the way to go. A sub crossed at 70-60Hz reduces the bass output demands on the B4Ns and theoretically improves mid-range output.

That's my story and I'm sticking to it! ;)